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Salt Glazing in a Catenary Arch Kiln

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Salt Glazing in a Catenary Arch Kiln SALT GLAZING IN A CATENARY ARCH KILN by ELDON LAVERN CLARK B. F. A., University of Kansas, 1953 A MASTER' S THESIS submitted in partial fulfillment of the requirements for the degree MASTER OF ARTS Department of Art KANSAS STATE UNIVERSITY Manhattan, Kansas 1966 Approved by: i#j w^,'. Major Professor ii TABLE OF CONTENTS INTRODUCTION 1 REVIEW OF LITERATURE 2 History of Salt Glazing 2 Technical Aspects of Salt Glazing .... 5 Kilns 17 MATERIAL AND METHODS 19 Construction of Catenary Arch Kiln 19 Operational Procedures 29 ANALYSIS OF FIRED WARE 39 Clay Body 39 Colorants 40 Salt Mixtures 42 CONCLUSIONS AND RECOMMENDATIONS 43 Conclusions 43 Recommendations 44 EVALUATION OF THESIS POTTERY 45 ACKNOWLEDGMENTS 85 REFERENCES .86 MfLD TV c ^ INTRODUCTION The purpose of this study was to determine the plausibility of salt glazing in a catenary arch kiln. The study was limited to kiln construction and its operation, and to ware production which characterized the simple, direct quality inherent in salt glazing. Background material was obtained from three, major sources: library collections of Kansas State University and the University of Kansas, personal correspondence with potters who have worked with salt glazing, and personal experience. The salt-glazing process is an inexpensive means of obtaining a hard, but handsome, glaze for stoneware. The salt-glazing industry flourished in Europe during the 17th and 18th centuries, and produced items such as ceramic utensils, beer mugs, and storage Jars. The industry was active in America during the colonial period. Today, however, salt glazing, on a large scale, is confined to industrial materials. Salt glazing presents unlimited possibilities to the studio potter for the production of ware which is intrinsically charming. Because the potter needs a separate kiln for salt glazing, the catenary arch design affords the potter a rugged, maintenance- free kiln. A personal, critical analysis has been given of this writer's pottery designed during the time of this research. REVIEW OF LITERATURE History of Salt Glazing The origin of salt glazing is vague, but most authorities agree that the process was discovered by accident. The stoneware industry was pros- perous during the 15th to the 17th centuries in Germany, and most of the early German salt-glazed ware dates from the 16th century; however, H. G. Schurecht (1943) states that the salt-glazing process dates to the 12th century in northern Germany around Aachen. During the 1600*8, salt glazing began in England, and it is believed that the vapor-glazing process came to America during the early colonial period. In his Primer, Salt Glazed Stoneware . Edwin A. Barber (1907) describes the styles, colors, and decorations of early German, English, and American salt-glazed ware. The earliest center of German salt-glazed ware was at Siegburg, near Bonn, in the 15th century. There, a coarse, brownish-gray stoneware was produced and incorrectly called Cologne ware because the market was in Cologne. The Siegburg ware shapes were basically tall, cylindrical wine bottles and globular jugs with hand- finished bases, deco- rated with medallions and biblical subjects. The glaze was usually very thin and sometimes absent. Yellowish-brown bodied jugs and wine bottles with reddish- brown, smooth glazes bearing dates of 1539, were produced at Raeren in Flanders. H. G. Schurecht, "Salt Glazing of Ceramic Ware," American Ceramic Society Bulletin . 1943, 22:45. I Frechen ware, decorated with grotesque masks and imitation coins, had a brown body and brown glaze. The wire markings on the base of the ware indicate that the ware was cut from the wheel, unlike the Siegburg ware which was torn from the wheel. Brown stoneware mugs and jugs, decorated with figures and geometric patterns in applied relief, from Kreussen, date from the middle of the 16th century. Gray clay-bodied mugs, bottles, and jugs, with incised and applied relief patterns, were manufactured at Hohr and Grenzhausen during the 17th, 2 18th, and 19th centuries. Hohr- Grenzhausen is among the few remaining 3 communities doing salt glazing today. Bouffioux ware became firmly established late in the 16th century in an area which is new* Belgium. The clay bodies were brown with irregular brown giazes and decorated with masks and medallions. Large and small barrels, kitchen utensils, and jugs made up the inventory of Bouffioux 4 ware. Salt glazing was introduced in England during the Elizabethan period, but it reached its height during the 18th century. John Dwight obtained from Charles II patents for the manufacture of stoneware, including salt glaze, for his pottery at Fulham. Fulham ware was styled in the manner of Frechen ware. In 1693, Dwight began legal action against Aaron, Richard, Edwin A. Barber, Salt Glazed Stoneware . 1906, pp. 12-13. 3 Angelo C. Garzio, "German Salt Glazing," Craft Horizons . March/ April, 1963, 23:20. 4 Barber, op., cit .. pp. 14-16. and Thomas Wedgwood for what Dwight claimed to be violations of his patents. The records of the suits show proof that ware of the Fulham style was pro- duced in Staffordshire before 1700. Staffordshire ware remains as the prominent example of English salt glaze. Barber describes English salt glaze this way: The term "salt glaze" has been applied to an English product, a true stoneware of white body, thin and graceful in appearance, so highly fired as to be translucent in its thinnest parts, covered with an exceedingly hard saline glaze, which first appeared in Staffordshire near the close of the 17th century. The desire to find ways of producing Chinese porcelain led Staffordshire potters to the production of a light colored, salt-glazed stoneware. In 1710, Thomas Wedgwood made a buff-colored ware decorated with raised designs. By 1720, Ashbury added calcined flints to a light-colored clay to develop a white clay which failed to imitate porcelain, but instead, he produced a hard, strong stoneware capable of being moulded with great fineness and precision. "Scratch ware," dated from 1740, was colored by incising designs on the ware and dusting it with powdered cobalt, or rubbing cobalt into the scratches. By 1750, salt-glazed "...teapots were often made in the most fantastic shapes such as houses, camels and pecten shells." By about 1770, the manufacture of white salt-glazed stone- ware had almost ceased, cream coloured earthenware having become firmly established by then. 8 Bernard Rackham, Early Staffordshire Pottery . 1951, pp. 19-27. 6 Barber, o£. cit. , p. 20. Griselda Lewis, EnAlish Pottery . 1956, explanations of figures 93-94. 8 Loc. cit. Although potteries were producing wares in the United States as early as 1684, it is unlikely that salt glazing was done for ten to thirty years 9 later. Early American salt-glazed products were ...ware of a rude and simple character, in the forms of crocks and jars and other utilitarian articles, entirely devoid of ornamentation save an occasional dash of blue or, in exceptional cases, a few roughly incised ornaments. •* Late in the 18th century, Paul Cushman manufactured stoneware near Albany, New York, which had a brownish body, and was limited in cobalt decoration. Most Early American salt-glazed ware had the brownish-gray body with the extensive use of cobalt blue decoration. Barber however, gives credit to a woman for combining artistic elements with utilitarian ceramic craft. It was reserved for a woman, however, to breathe the breath of artistic life into the body of American stoneware, and under her deft touch, guided by refined instinct and inventive genius, the old utilitarian forms were converted into new and graceful shapes.. .The honour of raising the humble manufacture of salt- glazed ware in this country to a place beside the finer ceramic arts belongs to Mrs. S. S. Frackelton. 12 Technical Aspects of Salt Glazing W, P. Rix listed important considerations which influence the success of salt glazing. 9 John Ramsay, American Potters and Pottery . 1949, p. 39. Barber, o£. cit . , p. 24. U Ibid .. p. 25. 12 Ibid., p. 27. ) (1) Since the action of salt takes place only on siliceous particles, highly siliceous clays are necessary. (2) The ware body must be at a point of incipient vitrification before glazing. (3) Once the surface of the ware has been vitrified, no further change in condition can take place no matter how much the temperature of firing or the quantity of salt is increased. (4) When salt is introduced into the kiln, the temperature will drop rapidly; therefore, salting should be done in series to allow the temperature to rise after each salting. (5) Some means of introducing water into the kiln at the time of salt- ing is necessary to provide for the union of water vapor and the free chlorine. (6) Cooling must be rapid to & dull red heat to prevent crystalliza- 13 tion, then slowed to prevent dunting. (Dunting— cracking of ware during kiln cooling period caused by strains between glaze and body. J. 0. Everhart (1930), in an effort to find ways to reduce the cost of production of sewer pipe, conduit, face brick, and building tile, used various concentrations of salt in slips (clay suspended in water) to produce a salt glaze. Salt glazing by the normal method of introducing salt into the kiln at the maturing temperature was restricted to periodic kilns. Everhart worked on a process of salt glazing in tunnel and chamber kilns, 13t "vf. P. Rix, "Notes on Vaporous Method of Glazing Pottery," Literature Abstracts of Ceramic Glazes . 1951, p. 301. as well. Initially, he applied sodium chloride alone on the ware, but found that too much volatilization took place before a proper temperature could be reached for the formation of glass. The salt alone caused a darkening of the surface, an undesirable feature for his experiment.
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